1. Field of Invention
The present invention relates generally to light sources utilizing light emitting diodes (LEDs). In particular, the present invention relates to aviation signal lights providing omnidirectional patterns, such as a runway edge light, obstruction light and similar, where requirements for specific light distribution across the pattern are mandatory.
2. Discussion of Relevant Prior Art
Signal lights such as airfield lights and aviation obstruction lights require certification by the government (Federal Aviation Authority) or international organizations (ICAO). These specifications identify photometrics in detail. For example, ICAO specifications for medium intensity flashing red obstruction lights call for peak intensity minimum 2000 candelas + or −25% at horizontal level and allow maximum intensity limited by 75% of peak at −1%, with beam spread 3°. Application of solid-state technology (LEDs) as a light source because of the low power consumption, long lifetime, and smaller and lighter-weight design, makes it possible to overcome major disadvantages of conventional light sources, such as incandescent and halogen lamps. However, the solid-state technology's total efficiency in a luminaire, in practice, does not exceed 60%. This is why the performance of LED-based signal lights depends on implanted optics, specifically secondary optics light transformers which transforms light emitted by LEDs into light patterns required by specifications. In order to increase LED luminaire performance up to 85% to 90%, non-imaging light transformers, refractive and reflective (including total internal reflection properties) can be implemented. The method of design based on use, both the specifics parameters of the particular light source (such as LED spatial light distribution) and required light distribution across the pattern as a light transformer's design parameters are described in detail in U.S. Pat. No. 6,543,911.